Fitbit Flex review

Can Fitbit's latest fitness tracker take on Jawbone and co?
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Fitbit Flex
By Fitbit
If you’re on the prowl for a fitness band, the Fitbit Flex is a well-balanced choice; a slick design and some solid activity tracking features - not to mention an affordable price - make this a strong, if not overly incredible, fitness contender.

  • Handy light notifications
  • Good price
  • Accurate tracking
  • Water resistent
  • App lacking
  • Fiddly charging process
  • Bland looking
  • No dedicated display

Following the success of the One, Fitbit has renewed its fight for wearable domination. But while the Flex is certainly sleek, can it out muscle the competition?

The Fitbit One, a pill-shaped fitness tracker that clipped onto your jeans, was a neat little device that wanted to get you on the path to a fitter, healthier you.

Essential reading: Fitbit Charge 2 | Fitbit Flex 2

The new Fitbit Flex kicks things up a gear, shifting your stats and tracking to your wrist and packing some clever new tricks to help speed you on your way to your fitness goals.

It's got some serious competition on its hands with the likes of the Nike Fuelband SE, the Jawbone UP24 and the Garmin Vivofit, but with an affordable price tag and bunch of features that push it beyond the humble pedometer, can Fitbit offer something its rivals can't?

Fitbit Flex review

Fitbit Flex: Features and design

When the Flex's LED panel lights up, it looks more like an ID tag from the year 2050 than the latest wearable innovation, but it's a sleek and mostly unobtrusive gadget, that's less likely to become a conversation piece.

Guide: Fitbit Flex tips and tricks

The band itself that straps this to your wrist is just a piece of plastic; those lights adorning the Flex face actually emanate from the Fitbit core, a small pill-like module resembling the Fitbit One, which sits inside. This can easily be taken out, and you'll need to remove it when it's time to charge.

Fitness tracker showdown: Fitbit Flex v Jawbone UP24

The Flex band comes in a rainbow of colour options and that interchangeable band means you can get all fashion and pair this with your Reiss shirt, those Blahnik heels or maybe just your Nike trainers.

With no display, you won't be doing a lot of interaction with the Fitbit itself. Unlike some of the competition you can't keep tabs on things like calorie count or steps on the Flex itself. You'll need to fire up the companion app to dig deeper into your vitals.

Interaction with you Flex is minimal; tap twice and the lights will appear to tell you how much progress you've made towards your goal; tap five times to tell the Flex you're about to catch some shut-eye and send it into sleep-tracking mode.

Wareable verdict: Fitbit Charge review

Once in sleep mode, not only will the Flex's sleep tracker monitor how well you've been snoozing, there's a built-in silent alarm to wake you gently. Sadly the Flex isn't smart like the Jawbone UP24, which tries to wake you when you're in your lightest sleep. Instead this just buzzes you back from dreamland at a specifically set time.

Finally, the Flex is water resistant, meaning it can survive a trip into the shower and a few splashes here and there, but it won't much like being taken scuba diving or for a triathlon training session down the local pool. You've been warned.

Fitbit Flex review

Fitbit Flex: Activity tracking

Drawing on its built-in accelerometer, the Flex monitors your footsteps taken and uses that to calculate distance travelled, calories burned, and how many minutes in the day you've been active.

That information can be sent straight to your phone using Bluetooth, without the need to plug the Flex into anything.

Handily, the Flex can tell when you're moving with more intensity than usual (say, a brisk walk) and will adjust the results to reward you accordingly. The lack of altimeter means it can't tell when you've climbed stairs or walked up a monster hill, which is a shame.

Accuracy-wise, the Flex is pretty much on par with its rivals, though it's also easier to fool into thinking you've done more work than you have with a few sneaky shakes of the wrist - something Nike was quick to fix with the second-gen Fuelband SE.

Still, the LED-based indicator (something that the Jawbone UP24 lacks) is one of the Flex's best features, and means you won't have to fish your phone out every time you want an update on your progress. It's not the most informative of displays, but it covers the basics.

Fitbit Flex review

Fitbit Flex: App

The Fitbit app is nice and simple, uninspiring but easy-to-use. The opening dashboard dishes up an overview of your steps, calories and the like, with access to a more detailed breakdown for each section with a quick tap.

The Flex definitely lacks some of the smarts of its rivals and requires you to enter a lot of your activity yourself. Irritating but something you'll want to do if you want your Flex to be more than a glorified step counter.

Doing all the basic stuff like adjusting goals and setting alarms is easy enough and you can also log your food intake - taking advantage of the app's barcode scanner - if you're feeling especially lazy. This last function is especially welcome, as the Fitbit food tracker isn't its strongest feature.

Fitbit Flex review

Fitbit Flex: Battery life

Depending on how you use the Flex, you'll get between five and seven days of use on a single charge. That's not too bad, matching the Jawbone UP24 and surpassing many others on the market. But it's not quite up to the Nike Fuelband SE - and it's miles off the Misfit Shine's four-month battery life or the Garmin Vivofit's year-long promise.

Like a of fitness bands and sports watches, frustratingly, you'll need to use the included USB dongle every time you want to charge it, which means an extra thing to throw in the bag when you're running out the door.

How we test

Kieran Alger


Kieran is a world record-setting runner and one of the UK's most experienced running journalists.

A constant tester of the latest fitness technology, he's always hunting for innovations that can make him run faster, further and generally be in better shape.

Kieran is often found wearing four GPS running watches at once. And to date he's tracked more than 50 marathons, 13 ultras and countless half marathons - including the Marathon Des Sables.

In 2022, he became the first person to run the river Danube from sea to source, a measly 1,830 miles in 66 days. And still had time to test running gear.

Kieran regularly takes running tech to the extremes for Wareable and the likes of Runner's World, Mens Health and Wired.

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